" split-wx=on|off (enable TCG split w^x mapping)\n"
" tb-size=n (TCG translation block cache size)\n"
" dirty-ring-size=n (KVM dirty ring GFN count, default 0)\n"
+ " eager-split-size=n (KVM Eager Page Split chunk size, default 0, disabled. ARM only)\n"
" notify-vmexit=run|internal-error|disable,notify-window=n (enable notify VM exit and set notify window, x86 only)\n"
" thread=single|multi (enable multi-threaded TCG)\n", QEMU_ARCH_ALL)
SRST
is disabled (dirty-ring-size=0). When enabled, KVM will instead
record dirty pages in a bitmap.
+ ``eager-split-size=n``
+ KVM implements dirty page logging at the PAGE_SIZE granularity and
+ enabling dirty-logging on a huge-page requires breaking it into
+ PAGE_SIZE pages in the first place. KVM on ARM does this splitting
+ lazily by default. There are performance benefits in doing huge-page
+ split eagerly, especially in situations where TLBI costs associated
+ with break-before-make sequences are considerable and also if guest
+ workloads are read intensive. The size here specifies how many pages
+ to break at a time and needs to be a valid block size which is
+ 1GB/2MB/4KB, 32MB/16KB and 512MB/64KB for 4KB/16KB/64KB PAGE_SIZE
+ respectively. Be wary of specifying a higher size as it will have an
+ impact on the memory. By default, this feature is disabled
+ (eager-split-size=0).
+
``notify-vmexit=run|internal-error|disable,notify-window=n``
Enables or disables notify VM exit support on x86 host and specify
the corresponding notify window to trigger the VM exit if enabled.
they are specified. Note that the 'id' property must be set. These
objects are placed in the '/objects' path.
- ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,offset=offset,readonly=on|off``
+ ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,offset=offset,readonly=on|off,rom=on|off|auto``
Creates a memory file backend object, which can be used to back
the guest RAM with huge pages.
The ``readonly`` option specifies whether the backing file is opened
read-only or read-write (default).
+ The ``rom`` option specifies whether to create Read Only Memory
+ (ROM) that cannot be modified by the VM. Any write attempts to such
+ ROM will be denied. Most use cases want proper RAM instead of ROM.
+ However, selected use cases, like R/O NVDIMMs, can benefit from
+ ROM. If set to ``on``, create ROM; if set to ``off``, create
+ writable RAM; if set to ``auto`` (default), the value of the
+ ``readonly`` option is used. This option is primarily helpful when
+ we want to have writable RAM in configurations that would
+ traditionally create ROM before the ``rom`` option was introduced:
+ VM templating, where we want to open a file readonly
+ (``readonly=on``) and mark the memory to be private for QEMU
+ (``share=off``). For this use case, we need writable RAM instead
+ of ROM, and want to also set ``rom=off``.
+
``-object memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave``
Creates a memory backend object, which can be used to back the
guest RAM. Memory backend objects offer more control than the
projects / mirror_qemu.git / blobdiff